Histology

Question 1

Circulatory system related systems (2)

Answer 1

Cardiovascular (blood vascular) system

Lymphatic vascular system

Question 2

Roles of cardiovascular system (4)

Answer 2

Transport of oxygen and nutrients to tissues
Transport of CO2 and other metabolic waste from tissues
Thermoregulation
Distribution of hormones and immune cells

Question 3

Basic layers of blood vessels (3)

Answer 3

Tunica intima - Single squamous epithelial cells supported by basal lamina and thin layer of connective tissue
Tunica media - Mostly smooth muscle where thickness varies
Tunica adventitia - Made of supporting connective tissue

Question 4

Elastic arteries (2)

Answer 4

Largest arteries like aorta

Due to many sheets of elastic fibres in tunica media to provide elastic recoil

Question 5

Arterioles (4)

Answer 5

Only one/two layers of smooth muscle
No adventitia
30 - 200 micrometers in diameter
Vital in controlling blood flow into tissues

Question 6

Capillaries (3)

Answer 6

Composed of endothelial cells and basal lamina
4 - 8 micrometers in diameter
Has pericytes at intervals outside basal lamina - connective tissue with contractile properties

Question 7

Capillary types (3)

Answer 7

Continuous - In muscle, connective tissue, lung, skin, nerve
Fenestrated - has 50 nanometer pores and found in gut mucosa, endocrine glands, kidney glomeruli
Sinusoidal/Discontinuous - Has large gaps for macromolecules and cells and found in liver, spleen and bone marrow

Question 8

Microvascular networks (2)

Answer 8

Small arterioles connect to a postcapillary venule through a network made up of metarterioles, thoroughfare channels and capillaries
Precapillary sphincters at the capillary beginning controls flow through the network

Question 9

Postcapillary venules (4)

Answer 9

10 - 30 micrometers in diameter
Endothelial cell-lined with thin layer of connective tissue and some pericytes
Vital sites for cell exchange in inflammation
When vessel has smooth muscle in tunica media they become venules (More than 50 micrometers in diameter)

Question 10

Veins (3)

Answer 10

Thin continuous tunica media with few layers of smooth muscle
Largest veins like VC have thick tunica adventitia with bundles of longitudinally orientated smooth muscle
Contains most of the blood in the body due to flexibility of accommodating expansion

Question 11

Valves in veins(2)

Answer 11

Located in small to medium sized veins

They are inward extensions of tunica intima

Question 12

Layers of the heart - In to out (3)

Answer 12

Endocardium
Myocardium
Epicardium

Question 13

Endocardium purpose and structure (3)

Answer 13

Lines entire inner surface of heart and valves
Endothelium => Basal lamina => Thin layer of collagen fibres => layer of denser connective tissue
Some areas contain subendocardium

Question 14

Subendocardium structure

Answer 14

Loose connective tissue containing blood vessels, nerves and branches of impulse conducting system

Question 15

Myocardium purpose and structure (3)

Answer 15

Thick middle layer
Contains bundles and layers of contractile cardiac muscle fibres
Individual muscle fibres are surrounded by collagenous connective tissue with rich capillary network

Question 16

Cardiac muscle cells structure (2)

Answer 16

Have a single (sometimes 2) central nucleus

Have intercalated discs passing across fibres at irregular intervals

Question 17

Importance of intercalculated discs

Answer 17

To anchor adjacent myocytes during muscle contraction

Allows spread of electrical activity

Question 18

Epicardium purpose and structure (3)

Answer 18

Outer layer of heart
simple squamous epithelium (mesothelium) => basal lamina => Fibroelastic connective tissue and adipose tissue (in some places)
Coronary vessels are typically embedded in adipose tissue

Question 19

Pericardium parts (2)

Answer 19

Fibrous

Serous

Question 20

Fibrous pericardium structure

Answer 20

Sac made of tough fibrocollagenous connective tissue

Question 21

Serous pericardium structure (2)

Answer 21

Mesothelium => Basal lamina => Connective tissue
The serous pericardium lines inner surface of fibrous pericardium (parietal serous pericardium) and surface of heart (visceral serous pericardium)

Question 22

How are the mesothelial layers separated

Answer 22

By a thin pericardial cavity containing 15-50ml of pericardial fluid for lubrication for heart movement

Question 23

Fibrous skeleton of the heart structure

Answer 23

Made of thick bands of fibrous connective tissue around the heart valves between the atria and ventricles

Question 24

Fibrous skeleton functions (3)

Answer 24

Supports valves
Provides attachment for cardiac muscle fibres
Electrically isolates atria from the ventricles

Question 25

Heart valves structure (3)

Answer 25

Endothelial layer => Basal lamina => layer of collagen and elastic fibres => lamina fibrosa (core dense irregular connective tissue)
Leaflets of valves are anchored by papillary muscles in wall of ventricle by chordae tendineae (collagenous strands that merges which lamina fibrosa)
No blood vessels are present

Question 26

Types of cardiac muscle cells (3)

Answer 26

Contractile cells
Pacemaker cells
Conducting cells

Question 27

Pacemaker cells (4)

Answer 27

4 - 8 micrometers in diameter
Embedded in more extensive connective tissue than contractile cardiac myocytes
Appear pale due to scarce amount of organelles
Contains few irregularly arranged myofibrils, little glycogen and no proper T-tubule system

Question 28

Purkinje fibres (4)

Answer 28

Larger than cardiac myocytes
They distribute the impulse so ventricular contraction is from inferior to superior
Found in subendocardial
Appear pale with clear centre due to abundant glycogen, no T-tubules, no intercalculated discs and sparse actin and myosin found at cell periphery

Question 29

Lymph vascular system (3)

Answer 29

System of thin walled vessels that drain excess interstitial fluid (lymph)
Lymph contains ions, lipids, proteins and occasional cells
Most of the lymph returns to capillaries and venous vessels

Question 30

How is lymph flow formed (4)

Answer 30

Smooth muscle
Hydrostatic pressure in tissues
Compression of vessels by voluntary muscle
Valves in vessels